The present invention relates generally to semiconductor fabrication, and more particularly, to systems and methods that mitigate altering of a chemical mechanical planarization pad compressibility and spatial uniformity and facilitate chemical mechanical planarization process stability.
Semiconductor device fabrication involves performing a variety of processes, procedures and operations in order to achieve a fabricated device. These operations include, but are not limited to, layering, doping, heat treatments, and patterning. Layering is the operation used to add layers of a selected thickness to a wafer surface. These layers can be insulators, semiconductors, conductors, and the like and can be grown or deposited by a number of suitable methods (e.g., chemical vapor deposition, sputtering, and the like).
Doping is the process that introduces specific amounts of dopants in the wafer surface through openings in surface layers. Two general techniques of doping are thermal diffusion and ion implantation. Doping is used, for example, to create active regions in transistors.
Heat treatments are operations in which a wafer is heated and cooled to achieve specific results. Generally, no additional material is added although contaminates and vapors may evaporate from the wafer surface. A common heat treatment is called an anneal which is employed to repair damage to crystal structures introduced by ion implantation.
Patterning is the operation that employs a series of steps that results in the removal of selected portions of added surface layers. After removal, a pattern of the layer is left on the wafer surface. The material removed can be in the form of a hole in the layer or a remaining island of the material. The patterning operation is also known by the names of photomasking, masking, photolithography, and microlithography.
Another important operation is chemical mechanical planarization (CMP), which can be employed in patterning operations. Generally, planarization is a process by which a wafer topography is made substantially flat or planar. CMP is a type of planarization process in which chemical and mechanical components are employed to planarize a wafer surface. Typically, a slurry comprised of a chemical component and mechanical components (e.g., abrasive particles) is flowed onto a wafer surface and a rotating pad is pressed against the wafer surface. The components chemically and mechanically remove portions of the wafer surface. The combined actions of the slurry and the rotating pad result in a polishing operation that can planarize the wafer surface.
In order to achieve a planar surface, it is important that the polishing pad be substantially spatially uniform with regard to compressibility. Non-uniformities can result in defects and/or a non-planar surface. Accordingly, it is desirable that a polishing pad be able to maintain its uniformity with regard to compressibility even after repeated use.
The following presents a simplified summary in order to provide a basic understanding of one or more aspects of the invention. This summary is not an extensive overview of the invention, and is neither intended to identify key or critical elements of the invention, nor to delineate the scope thereof. Rather, the primary purpose of the summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention includes a polishing pad that can facilitate process stability, extend length of use, and mitigate process non-uniformity and process induced defects for chemical mechanical planarization processes. The polishing pad of the present invention is a composite of a top pad and a sealed sub-pad. The sealed sub-pad has a sealing mechanism that mitigates liquid penetration into the sub-pad thereby maintaining a substantially spatially uniform compressibility of the sub-pad and the polishing pad and extending a useable life of the polishing pad.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects and implementations of the invention. These are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.